One common feature of the modern computer interface is a mechanism for moving a cursor or pointer across the computer's display. For stationary computers the “mouse” is the most common pointing mechanism. A related role for the mouse is to provide a method for attaching importance to certain pointer locations. Accordingly, mice universally provide at least one button to perform this task.
Because of space and weight constraints, portable “laptop” or “notebook” computers often use a miniature isometric joystick in the role of a pointing device. FIG. 1 shows an isometric joystick 100 manufactured by Synaptics, Inc. When installed in a computer, the lower portion 110 of the joystick is hidden below the computer's keyboard with the nub 120 typically protruding between the “G” and “H” keys.
The three dimensions in which the joystick conventionally measures input force are labeled on the axis 130 shown in FIG. 1. Force in the xy plane parallel to the work surface is used to position the cursor. Force in the direction perpendicular to the work surface, z, is used to perform selection operations analogously to those performed by the primary mouse button.